不锈钢在扭转/拉伸复合载荷下的低周疲劳裂纹扩展

LOW CYCLE FATIGUE CRACK PROPAGATION IN STAINLESS STEEL UNDER COMBINED TORSION AND TENSION

研究了从SUS316NG不锈钢圆棒试样的环状预裂纹开始的低周疲劳裂纹扩展行为,分析了扭转/拉伸复合加载时不同载荷比对弹塑性疲劳裂纹扩展的影响.用J积分的指数方程表达了简单加载及复合加载的裂纹扩展速率.对于同样的J积分范围值,Ⅰ型载荷下的裂纹扩展速率最高,而Ⅲ型载荷下的速率最低.裂纹断口在高应力水平下为宏观平坦,在复合加载条件下的疲劳断口上观察到了疲劳条痕,同Ⅰ型加载条件下的相同,疲劳条痕间距与裂纹扩展速率二者数值相等.

Low cycle fatigue crack propagation tests were conducted on a circurnferentially precracked round bar of a stainless steel under various combinations of cyclic torsion and tension. The crack propagation rate was, expressed as a power function of J integral range for both single and mixed mode. For the same J-integral range, the mode I propagation rate is the highest and the mode III one is the lowest. The fatigue fracture surface is macroscopically flat under the conditions of excessive plasticity. Striations were observed on the fatigue fracture surface under mixed mode loading, and their spacing value is equal to the crack propagation rate value, the same as in mode I case.